This invention relates to a method and circuit for driving power transistors in a half bridge configuration from control signals referenced to any potential between the line voltage and the line voltage return. For example, the present invention is applicable to power MOSFETS arranged in a half bridge configuration. It is equally applicable to other types of transistors. The invention also relates to an integrated circuit driver chip incorporating the circuit.
There is a need for an interface circuit between power transistors in a half bridge configuration and the control signals for the power transistors. There is especially a need for such an interface circuit which can couple the power transistors to control signals referenced to any potential between the voltage supply line for the power transistors and the return. There is furthermore a need for such a circuit which can be integrated in a single driver chip with other driver functions.
In the prior art, the most common cases are where the control signals are referenced to the return, to the line voltage or to a mid point between the line voltage V.sub.L and the return -V.sub.L. FIG. 1 of this application shows an example where the control signals are referenced to the mid point between the line V.sub.L and return -V.sub.L. In this case the mid point between the line and return is ground or V.sub.ss. In the circuit of FIG. 1, all control signals must be referenced to ground or V.sub.ss.
It would be advantageous if a circuit could be provided wherein the control signals could be referenced to any potential between +V.sub.L and -V.sub.L.